Abrha mulu article 1

International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064

Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438

Volume 4 Issue 3, March 2015

www.ijsr.net Licensed Under Creative Commons Attribution CC BY

Impact of Slaughterhouses Effluent on Water Quality

of Modjo and Akaki River in Central Ethiopia

Abrha Mulu*1, Tenalem Ayenew

2, Shifare Berhe

3

1Deparment of Chemistry, College of Natural and Computational Sciences, Aksum University, Ethiopia 2Department of Earth Science, College of Natural Science, Addis Ababa University, Addis Ababa, Ethiopia

3Deparment of Chemistry, College of Natural and Computational Sciences, Jigjiga University, Ethiopia

*Corresponding Author: Abrha Mulu Hailu, E-mail: [email protected] or [email protected]

Phone: +251-913499472, Affiliation organization: Aksum University, Axum, Ethiopia, P.O.B. 1010

Abstract: The objective of this study was investigating the impact of effluents of Kera and Luna slaughterhouses on the water quality of

receiving Rivers Akaki and Modjo respectively. Water samples from effluents of both slaughterhouses and both Rivers were examined

using standard procedure over the duration of two months period of dry season. It was found that except temperature and pH, the levels

of DO, TS, TSS, BOD5, COD, NH3-N, NO2--N, NO3

--N, S-2, SO4-2, PO4-3, TP, FC, TC and FOG of both rivers and both effluents did not

comply with standards of the country. Again the addition of discharges has caused many fold increase in most of the analyzed parame-

ters at downstream of both rivers. The result has revealed that there was an adverse impact on the physiochemical and bacteriological

characteristics of the receiving rivers as a result of the discharge of these effluents. There is a need of remediation of both Rivers as well

as an intervention of regulatory bodies to ensure production of high quality treated final effluents by the slaughterhouse industries.

Keywords:-Bacteriological, Effluent, Impact, Physicochemical, Rivers, Slaughterhouses, Water quality

1. Introduction

Freshwater is a scarce resource, essential for agriculture, in-

dustry, and human and animal life existence. We depend on

our streams and rivers to deliver much of these water uses.

Without adequate quantity and quality of freshwater sustain-

able development will not be true for all countries of our

globe. In Ethiopia from the increasing human population,

uncontrolled urbanization and waste disposal cause serious

quality degradation of surface waters. Now a day’s water

pollution from disposal of industrial wastewater is becoming

an environmental concern in Addis Ababa city and its vicini-

ty areas. Of these industries slaughterhouse industries such as

Kera slaughterhouse in Addis Ababa and Luna slaughter-

house in Modjo are exemplary. Slaughterhouse industries

consume large amount of water resource for washing of car-

casses after hide removal from cattle, goats and sheep; car-

cass washing after evisceration; equipment and facilities

washing; cooling of mechanical equipments. These activities

result to generate large amount of wastewater along with

other by-products.

Untreated slaughterhouse wastewater comprises a mixture of

fats, proteins and fibers, resulting in a high content of organic

matter and causes a contaminating effect to the rivers and

sewage systems. It also increases nitrogen, phosphorus, sol-

ids and BOD5 levels of the receiving water body, potentially

leading to eutrophication [1,2,3, and 4]. It has been reported

that discharge of large quantities of wastewater is common

environmental issue to all slaughterhouses [5]. However,

untreated effluent of Kera (in Addis Ababa) and partially

treated effluents of Luna slaughterhouse (in Modjo) from the

thousands of animals slaughtered daily throughout the year

flows into Little Akaki River and Modjo River, respectively.

These effluents may cause pollution over the rivers and also

create other environmental stresses in the downstreams and

nearby residential areas.

It is also reported that surface water bodies in developing

countries are under serious threat as a result of indiscriminate

discharge of polluted effluents from industrial, agricultural,

and domestic activities [6]. Surface waters in Addis Ababa

and Modjo are also not protected from such problem. As in-

dicated by Samuel Melaku et al [7]. Little Akaki River water

has been polluted because of industrial and intensive agricul-

tural practices as well as indiscriminate disposal of domestic

wastes. These situations have also been true to Modjo River

[8]. However the contribution of the effluents of slaughter-

house industries is not left known. So that knowing the effect

of slaughterhouse effluents on the water quality of the receiv-

ing rivers is essential. Therefore, this study aimed at investi-

gation of the impact of the untreated and partially treated

discharged slaughterhouses (Kera and Luna) effluents on the

water quality of the receiving water bodies, Akaki and Modjo

Rivers respectively.

2. Materials and Methods

2.1 Description of Study Area

The study areas were two rivers, Akaki and Modjo River

found in central Ethiopia. Both Rivers are tributary of the

Awash River and located in Addis Ababa city and Modjo

town, in the central rift valley of Ethiopia respectively. Akaki

River drains to the western part of the city. Addis Ababa, the

capital city of Ethiopia is found at the central part of the

country. Modjo town is the administrative center of Lomie

Woreda and is located in the East Shewa Zone of the Oromia

Regional State and 75 km Southeast of Addis Ababa. Those

rivers are receiving effluents of Kera and Luna slaughter-

houses (Figure 2 and 3) their location map is as shown in

Figure 1.

Paper ID: SUB152103 899

http://en.wikipedia.org/wiki/Ethiopia

http://en.wikipedia.org/wiki/Misraq_Shewa_Zone

http://en.wikipedia.org/wiki/Oromia_Region

http://en.wikipedia.org/wiki/Oromia_Region





Figure 1: Location map of Akaki River (A) in Addis Ababa and

Modjo River (B) in Modjo

Figure 2: Discharge of partially treated waste water in to Modjo

River

Figure 3: Direct discharge of untreated Kera slaughterhouse

effluent in to Little Akaki River

2.2 Sampling Techniques

Triplicate sampling was conducted from January to February,

2011. Nine water samples designated by P1 to P5 (Luna

slaughterhouse and Modjo River) and K1 to K4 (Kera slaugh-

terhouse and Akaki River) were collected from both sites.

The types of samples were raw effluent (from both slaughter-

houses); treated effluent (only from Luna slaughterhouse)

and river water (effluent receiving water bodies in both sites).

Each of these sampling points are clearly described in detail

in Table 1.

Table 1: Description of sampling points location of the two sites

Name of the

Site

Designation Type of water sample

Akaki river

and Kera

slaughter-

house

K1 Raw wastewater

K2 Discharge point (mixing point )of

slaughterhouse wastewater with Little

Akaki River

K3 Upstream of Little Akaki River (above

the discharge point)

K4 Downstream of Little Akaki River

(below the discharge point )

Modjo

River and

Luna

slaughter-

house

P1 Raw wastewater

P2 Treated Wastewater leaving the biolog-

ical wastewater Lagoon (Outlet of

wastewater Lagoon)

P3 Discharge point (mixing point) of

slaughterhouse effluent with Modjo

River

P4 Upstream of Modjo River (above the

discharge point)

P5 Downstream o of Modjo River (below

the discharge point)

2.3 Slaughterhouses Wastewater Sampling

Triplicate composite samples of raw effluent were collected

from both sampling sites designated as P1 and K1 from Luna

and Kera slaughterhouses, respectively. In addition to this, in

the case of Luna export slaughterhouses a treated wastewater

sample i.e. effluent passing through the three floatation and

sedimentation chambers, and leaving the wastewater treat-

ment lagoon (P2) were also collected, but not from the Kera

slaughterhouse since it does not have any treatment facilities.

The triplicate samplings were collected from both sites dur-

ing four hours of production time two weeks interval. The

samples from each period during four hours were mixed to

produce half to one half liter representative samples in each

sampling date. Each sampling points location map is dis-

played in Figures 4 and 5.The reason for the selection of four

hour is in order to produce representative samples. The selec-

tion of dry season and two weeks gap were in order to pro-

duce average data on the characteristics of those slaughter-

houses by taking in to consideration the time limit given to

complete this work.

Figure 4: Location map of each sampling points of Kera

Slaughterhouse and its effluent receivingLittle Akaki River






Figure 5: Location map of each sampling points of Luna

slaughterhouse and its effluent receiving Modjo River

2.4 River Water Sampling

Water samples from the effluent receiving water bodies i.e.

Modjo River, receives partially treated effluent from Luna

slaughterhouse and Little Akaki River, receives untreated

effluent from Kera slaughterhouse, were also collected by

little modification of the techniques used by EPA for prelimi-

nary analysis of selected industry effluents and the respective

receiving streams in Addis Ababa [9]. Modification was done

sampling from the discharge points into the rivers in addition

to samples from up streams and down streams of the rivers.

Water samples from those rivers were collected at the dis-

charge points (mixing points), upstream and downstream of

the discharge points in both rivers during the sampling pe-

riods of the wastewater. Six samples were collected from

both rivers i.e. P3, P4, and P5 along the Modjo River course and

samples K2, K3 and K4 along the Little Akaki River course as

displayed in the map (Figure 4 and 5) above.

P3 and K2 samples were slaughterhouse effluent mixing points

into the Rivers which were designated as 0 meter distance. P4

and K3 were collected at a distance of 10 to 15 meters upstream

of P3 and K2 respectively, while P5 and K4 were taken at a dis-

tance of 50 to 100 meters downstream of the corresponding

discharge point. The upstream and downstream sampling

points were carefully placed base on the rivers flow and en-

trance of other sewer lines to the rivers. In all sampling

points three 500 ml of grab water samples were collected

then all the three bottles were mixed to produce 1500 ml po-

lyethylene bottle of composite samples to reduce the analyti-

cal cost.

At each sampling points samples were collected in one po-

lyethylene bottles and two glass bottles. The two glass bottles

were used to collect samples for bacteriological and FOG

analysis. The polyethylene bottles are used for the rest physi-

cochemical parameters. All the bottles were previously

washed with detergent and further rinsed with deionized wa-

ter prior to usage. Finally, before sampling was done, the

bottles were rinsed with the water sample at the point of col-

lection. Samples for bacteriological analyses were kept in

well capped glass bottles that have been sterilized in an au-

toclave for 15 minutes at 121ºC. All samples were brought to

laboratory within ice box for physicochemical and bacterio-

logical test and analyzed as soon as possible after sampling.

In general, Sample collection and handling procedure were

performed according to the standard procedures recommend-

ed by APHA [10].

2.5 Physicochemical and Bacteriological Analysis of

Water and Wastewater Samples

The analyses of slaughterhouse wastewater and river water were

done both in situ and laboratory as explained below.

Onsite water analysis

The parameters such as conductivity (EC), temperature, pH,

turbidity and dissolved oxygen (DO) of the wastewater and

rivers were measured immediately on the sampling sites. It

was done using a conductivity meter (Wagtech International

N374, +M207/03IM, USA) to measure conductivity (EC),

portable DO meter (Hach P/N HQ30d, Loveland. CO, USA)

to measure both the dissolved oxygen and temperature, a

portable pH meter (Wagtech International N374,

M128/03IM, USA) was used to determine pH and Jackson

Candle Turbidimeter (in JTU) to measure turbidity. These

equipments were calibrated one day before each sampling

period.

Laboratory water analysis

The Chemical oxygen demand (COD), color, nitrate nitrogen

(NO3--N), ammonia nitrogen (NH3-N), nitrite nitrogen(NO2-N),

Total phosphorus (TP), Orthophosphate (PO4-3

), Sulfide (S-2

)

and Sulfate (SO4-2

) were measured by using spectrophotometer

(Hach model DR/2400 portable spectrophotometer, Loveland,

USA) according to Hach procedures [11]. Fat, oil and grease

(FOG), Five-day biochemical oxygen demand (BOD5), total

solids (TS), total suspended solids (TSS), Total coliform (TC)

and Fecal coliform (FC) were determined using the standard

methods of APHA [10]. Except for the FOG determination,

which was done in the JIJE Laboglass analytical service la-

boratory, Addis Ababa, all the parameters analysis were done

in the Environmental Science Program Laboratory, College

of Science, Addis Ababa University.

Data analysis

The obtained data were analyzed by using SPSS version 16.0

and origin version 8.0 softwares, and microsoft office excel.

3. Results and Discussions

Physicochemical and Bacteriological Characteristics of

Slaughterhouse Wastewater

Wastewater characteristics based on the analysis of the com-

posite sample from raw (untreated) wastewater of both

slaughterhouses are shown in Table 2. This Table summarizes

the mean, range and standard deviation of the physicochemi-

cal and bacteriological properties of wastewater of both

plants. Except for fat, oil and grease (FOG) was analyzed in

only one sample of the three sampling period, all the rest

parameters were analyzed in each sampling period.






Table 2: Average physiochemical and bacteriological characte-

ristics of the raw slaughterhouse wastewater and outlet effluent

discharged in to rivers

Parameter Mean + SD and range of raw

wastewater

Mean of outlet

effluent discharged

in to rivers

Kera Luna Kera Luna

pH 7.3+0.43

(6.8₋7.6)

7.24+0.74

(6.81₋8.108)

7.30 6.81

Tempera-

ture ( )

26.55+6.84

(21.85₋34.4)

28.12+7.27

(22.36₋36.3)

26.55 22.09

EC

( Scm-1)

1614.66+166.1

(1452₋1784)

1251.33+160.0

5

(1116₋1428)

1614.66 3850

Turbidity

(JTU)*

566.66+28.86

(550₋600)

436+172.12

(238₋550)

566.66 160.33

TS (mg/L ) 7885.33+4537.94

(2658₋10814)

3246+2099.52

(850₋4764)

7885.33 1176

TSS

(mg/L )

3835.33+2072.57

(1856₋5990)

1111+811.84

(260₋1877)

3835.33 125.66

Color

(TCU)

19733.33+18941.3

(8400₋41600)

1682+1118.37

(391₋2355)

19733.33 728.66

TP

(mg/L )

202+37.72

(160₋233)

55.4+13.20

(42.4₋68.8)

202.00 61.73

PO4-3

(mg/L )

67.33+27.06

(44₋97)

13+3.60

(10₋17)

67.33 28.26

Nitrite

(mg/L )

1513.33+393.10

(1220₋1960)

315+78.58

(245₋400)

1513.33 49.33

Nitrate

(mg/L )

1450+1255.74

(720₋2900)

615+121.34

(515₋750)

1450.00 13.66

Ammonia

(mg/L)

103.33+57.79

(41.5₋156)

41+5

(36₋46)

103.33 345.66

Sulfate

(mg/L )

693.33+70.23

(620₋760)

290+110

(180₋400)

693.33 31.33

Sulfide

(mg/L )

1.83+0.53

(1.51₋2.45)

0.24+0.31

(0.04₋0.6)

1.83 0.14

DO

(mg/L )

3.75+0.92

(2.7₋4.44)

4.73+0.69

(4.32₋5.53)

3.75 0.97

COD

(mg/L )

11546.67+4130.19

(6900-14800)

4752.66+1156.

27

(3538-5840)

11546.66 431.66

BOD5

(mg/L )

3980+1055.13

(2990-5090)

2110+602.24

(1420-2530)

3980.00 177.33

FOG

(mg/L )

1825.31 1019.6 1825.31 344.76

FC(cfu/100

mL)

2.08 x105±5.460

x104

1.35x106±3.722

x105

TC(cfu/100

mL)

1.35 x106±3.722

x105

4.40x106±1.114

x106

N.B: The value in parenthesis in the above Table is the range of the

corresponding parameter

*JTU: Jackson turbidity unit

4. Slaughterhouse Effluent Impact on the Qual-

ity of Receiving Water Bodies

The data obtained can be believed to provide enough infor-

mation regarding the impact of the slaughterhouse effluent on

the hydrosphere to which the effluent is released. Human

beings and other animals that might use the water contami-

nated with slaughterhouse effluent are highly exposed (sus-

ceptible) to various types of health problems. The results of

the physicochemical and bacteriological parameters assess-

ment of both rivers are discussed below.

As explained in the above discussion pH is the indicator of

acidity and alkalinity status of water. The mean values of

upstream of both rivers were identical, which were slightly

basic with pH value 7.47 and 7.46 for Akaki River and Mod-

jo River respectively. These values were within the Ethiopian

drinking water standard limit 6.5-8.5 [12]. However, a slight

drop in mean pH value to 6.84 (Akaki River) and 6.91 (Mod-

jo River) at discharge points and 7.33 (Akaki River) and 7.41

(Modjo River) at the downstream were observed. This could

be attributed to the addition of the slaughterhouse effluents

along with the eroded soil and trash materials end up in these

rivers. But these change is not serious still the pH values of

both rivers remain within the Ethiopian drinking water stan-

dard limit and may not cause an adverse effect on the surviv-

al of aquatic organisms.

Temperature is the most important factor which influences

the chemical and biological characteristics of the aquatic sys-

tem. The temperatures of both rivers in each of the sampling

points varied from 21.4 to 24.84° C in Little Akaki River and

from 19 to 29.9 ° C in Modjo River. These values were found

within the range of surface waters temperature, 0° C to 30° C

[13]. The Little variation in each sampling points of the rivers

could be influenced by air circulation, flow and depth of the

water body [13]. It is obvious that unpolluted water is a co-

lorless so that Color can be used as one parameter in measur-

ing pollution status of water. The mean color values in the

discharge point, upstream and downstream of Little Akaki

River were 2030, 676, and 1530 units Pt-Co respectively.

Similarly, the color levels in the discharge point, upstream

and downstream of Modjo River were 523.33, 116, and

1973.66 units Pt-Co respectively. The increment in the down-

stream of both rivers was arising from discharge of slaugh-

terhouses wastewater dominated by blood and other organic

substances. Regardless of the sampling points, in both rivers

the levels of color were found above the WHO drinking wa-

ter guidelines limit (less than15 TCU) [14].

As regard to the means of total solids (TS), total suspended

solids (TSS), and turbidity values of both slaughterhouses

outlets were tremendously high as present in Table 2. Upon

introduction of these effluents into the rivers, the values had

been changed from 725.33 mg/L to 913.33 mg/L of TS in

Akaki River and 932.00 mg/L to 1504.66 mg/L of TS in

Modjo River; again from 304.33mg/L to 456.00 mg/L of TSS

in Akaki River and 154.00 mg/L to 323.00 mg/L of TSS in

Modjo River. Similarly, turbidity values had been changed

from 350.00 JTU to 420.00 JTU and 134.66 JTU to 285.53

JTU in Akaki River and Modjo River respectively. The in-

crement in the magnitude of these parameters at downstream

compared to the values at upstream is due to the influence of

the slaughterhouses wastewater on the receiving water bo-

dies. The presence of such high concentration of TS, TSS and

turbidity reduce the aesthetic value of the receiving water

bodies and also reduce DO of the river.

Similarly, the conductivity (EC) values also changed

from1245.33 μScm-1

to 1290.33 μScm-1

(Akaki River) and

1564.66 μScm-1

to 2676.66 μScm-1

(Modjo River). However, the

conductivity of most freshwaters ranges from 10 to 1, 000 μScm-

1 and in polluted water may exceeds 1,000μScm

-1 [13]. The EC

values obtained in both rivers also exceeds 1,000μScm-1

, indi-

cates that both rivers are polluted. The addition of the slaugh-






terhouses effluent exacerbates the situation. However, it has

been observed that the rivers being used by the nearby resi-

dents for irrigating of vegetables (Little Akaki River) and

bathing in Modjo River (Figure 6).These may cause human

health risk.

Figure 6: Modjo River used for bathing by the nearby resident

Dissolved oxygen is a very important parameter for the sur-

vival of aquatic organism and is also used to evaluate the

degree of freshness of a river. However, the DO concentra-

tion of both rivers examined (Table 4) were found below the

value that can support survival of aquatic organisms (5 mg/L)

as well as at a concentration that can lead to death for most

fish, below 2 mg/L [13].

Again the dissolved oxygen concentrations of both rivers

follow dissimilar trends (Figure 7). The DO levels of the up-

stream of both rivers were lower than that of the discharge

points, and these values also found below the value of down-

stream in Modjo River. These situations were caused due to

difference in flow of the water throughout the course of riv-

ers. The flow in the upstream of Modjo River was extremely

slower than its discharge point and downstream. This might

have led to be hardly aerated. On the other hand the dis-

charged effluent from the slaughterhouses may be reaerated

on its way of travel before mixing with the corresponding

river; this may contribute little increment in DO concentra-

tion at the discharge point. Besides flow variation, DO in the

upstream of both rivers might be depleted due to the conti-

nuous discharge of effluent from different sources such as

both municipal and industrial wastes of Addis Ababa city into

Little Akaki River [7]. and Modjo town into Modjo River [8].

Both biological oxygen demand and chemical oxygen de-

mand are highly related to DO as well as to each other. Since

BOD and COD directly affect the amount of DO in the river.

Both BOD and COD are important water quality parameters

and are very essential in water quality assessment [13]. These

are important parameters, used to determine whether a water

body is polluted or not. The higher the BOD and COD values

would be depleting the higher DO concentration in the re-

ceiving rivers by organic and inorganic pollutants present in

the effluents. The mean BOD and COD concentrations of

both rivers along with the outlets of both slaughterhouses

follow similar trend as illustrated in Figure 8. The lowest

values were recorded in the Luna slaughterhouse outlet and

the highest values in Kera slaughterhouse outlet. These val-

ues were large enough to cause damage on the normal func-

tions of the receiving rivers. These magnitudes were much

higher at Little Akaki River than Modjo River. This is attri-

buted to the difference in the concentration of effluent dis-

charged from both slaughterhouse industries to the corres-

ponding rivers.

Figure 7: Trends of DO concentration in both rivers

Figure 8: Trends of average COD and BOD concentration in

both rivers

The observed BOD and COD levels (Figure 8) were also

noticed to be above the WHO limit value for undisturbed

river which is less than 2mg/L and 20 mg/L [15]. These high

levels of BOD and COD could deplete the DO in the water

system. The result indicated that the water bodies sampled

were deteriorated due to continuous discharge of untreated

and partially treated slaughterhouse effluents.

The COD and BOD also have a direct relationship with TS

and turbidity throughout the course of both rivers since these

parameters increased or decreased in similar manner in each

sampling points of the rivers as shown in Figure 9 and 10. It

showed that water with high amount of TS and turbidity

could lead to high concentration of COD and BOD. Moreo-






ver, the presence of high concentration of TS and turbidity

also reduce the aesthetic value of both rivers.

Figure 9: Trends of Turbidity, TS, COD and BOD in Modjo

River

Figure 10: Trends of Turbidity, TS, COD, and BOD in Little

Akaki River

The average orthophosphate (PO4-3

) and total phosphorus

(TP) level ranging from 0.46 - 67.33 mg/L and 0.85 - 202

mg/L respectively in the entire sampling points. The major

peaks in orthophosphate and total phosphorus concentrations

were found at the outlets of both slaughterhouses, followed

by a decline from the discharge points to the downstream and

the lowest concentration were registered in the upstream of

Modjo River. However, a slight deviation of orthophosphate

and TP was observed in Akaki River (Figure 11). This devia-

tion might happen from the variation of the organic matter

decomposition which accelerates the conversion of organical-

ly bound phosphorus to orthophosphate at the downstream of

this river. Discharges of the slaughterhouse effluents with

high phosphate content might be responsible for the in-

creased levels observed in Modjo River. Possible sources of

phosphate and orthophosphate might be from the phosphorus

rich liquid and solid by-products of slaughterhouses activities

such as blood, bone and manure. In addition to this extensive

uses of phosphate based detergents for cleaning purposes in

these slaughterhouses industries may also have considerable

contribution. Total phosphorus levels in undisturbed rivers

are generally less than 25μg/L, phosphorus concentration

greater than 50μg/L are attributed to human activities and

contamination rise to excessive growth of algae [16]. So that

the effluent discharged from both slaughterhouses was

enough to cause eutrophication on receiving rivers.

Figure 11: Mean concentrations of orthophosphate and TP in

both sites of outlets and receiving streams

The other nutrients like ammonia nitrogen and nitrite nitro-

gen follow similar trend as orthophosphate and TP in both

sites. However, the nitrate nitrogen concentrations follow

different trend in both sites (Figure 12). In the case of Kera

site nitrate major peaks were found at the slaughterhouse

outlet and followed by a decline at the upstream (Little Akaki

River) and then lowest concentration was registered at the

discharge point. However, higher nitrate concentration was

observed at upstream of Little Akaki River than downstream

and discharged point during the sampling periods. It is sug-

gested probably due to diffused sources (non point sources)

of pollution entering into the receiving water body (Little

Akaki River) such as nearby latrines of the residential and

commercial areas, industrial discharges in the far upstream of

the river. Where as in the second sampling site higher con-

centration of nitrate was observed at the downstream, fol-

lowed by a decline at the discharge point and further decrease

at the outlet of the slaughterhouse, and the lowest concentra-

tion at the upstream of Modjo River (Figure 12). The ob-

served unusual trend probably due to the end product of

aerobic decomposition of organic nitrogenous matter is ni-

trate. So that its concentration is expected maximum at high-

ly aerated zone of the river (since the downstream of Modjo

River is well aerated than its downstream as discussed

above). Its present in high concentration in drinking water

has a health risk for young children causing methemoglobi-

naemia (blue babies syndrome) [16].






Figure 12: Average nitrate nitrogen concentrations of both

slaughterhouse outlets and receiving rivers

The mean sulfide level of both rivers was higher than the

WHO taste and odor thresholds limit value estimated be-

tween 0.05 and 0.1 mg/L [16]. This result may be due to the

very low dissolved oxygen level of both rivers which led to

subsequent reduction of sulfate to sulfide by bacterial action.

The mean values in Modjo River were found unexpected

trend. This could be due to the flow variation in the course of

the river that is the upstream of Modjo River had relatively

low speed of flow led to be less aerated and subsequent re-

duction of sulfate to sulfide. However, sulfide can only oxid-

ize to sulfate in well aerate zone of the river which led to low

concentration of sulfide in the downstream and discharge

point of the river which was a little bit well aerated (Figure

13).

The mean sulfate levels of upstream discharge point and

downstream of both rivers is displayed in Figure 14. These

levels were higher than the natural background sulfate levels

of 1.0-3.0 mg/L reported for unpolluted rivers [15]. The ele-

vated levels of sulfate upstream of Little Akaki River may be

attributed to increased utilization of cement for building and

construction purposes around this area since the river is sur-

rounded by residential and commercial buildings and due to

flow variation in Modjo River. In polluted waters the dis-

solved oxygen is very low and sulfate is readily reduced to

sulfide causing noxious odors [17]. The fat, oil and grease

level in both rivers was observed that at the upstream of

Akaki River (316.83 mg/L) was considerably higher than that

of Modjo River (169.07 mg/L). This may be due to the urban

runoff which conveys great amount of oil and grease from

various automobile workshops and oil depot sited further

upstream of the river. These levels became considerably ele-

vated in the discharge point of both rivers suggesting possible

contribution from slaughtering processes, while the values

were decreased downstream due to the dilution effect of the

rivers. FOG have a high BOD and discharging of it creates a

thin film on the surface of water, which impedes the ex-

change of air and water, thereby increasing oxygen demand

[18].

Another concern arising from slaughterhouse effluent dis-

charge to rivers is the possibility of pathogenic bacteria in the

river. Fecal coliform and total coliform bacteria were used as

indicators of bacterial contamination of the rivers. The data for

fecal coliform and total colifrom bacteria of both rivers is pre-

sented in Table 3.

It was observed that in the case of Little Akaki River the

highest count was found rather than the Kera slaughterhouse

outlet. High bacteriological population in this river may re-

flect the input of microorganisms from extra sources mainly

municipal sewer lines entered to the river. However, the addi-

tion of the slaughterhouse effluent aggravates the problem.

The bacteria loads were generally high in all samples. This

would be limit variety uses of the rivers water including

recreation, drinking water sources, and aquatic life and fishe-

ries.

Figure 13: Average concentration of sulfide in both rivers

Figure 14: Average Sulfate concentrations of both rivers

Table 3: Average bacteriological load in both rivers

Ri River Coliform (cfu/100mL) Discharge point Upstream downstream

Modjo River FC

9.73 x104 ± 1.102 x104 3.77 x104 ±4.447 x104 4.93 x104 ± 3.950 x104

TC 3.58x105 ± 4.131 x104 4.73 x104 ± 5.508 x103 1.03 x105 ±6.531 x104

Little Akaki River FC 6.83x106 ± 4.726 x105 6.70 x106 ± 4.583 x105 6.97 x106 ±4.933 x105

TC 2.13 x107 ±1.528 x106 2.10 x107 ± 2.000 x106 8.73 x107 ±1.149 x108






5. Comparison of Slaughterhouse Effluent Dis-

charged With Standard Permit Limits and

Both River With Each Other and Drinking

Water Quality Standards

The relative concentrations of pollutants of both slaughter-

house effluent with standard permit limits and both rivers

water quality with WHO and Ethiopian drinking water quali-

ty illustrated in Table 4. It was observed that concentration of

most of pollutants were highest at the discharge points due to

the increased discharges of both slaughterhouses wastewater

and fall down at the down streams due to the assimilation and

dilution effects of the rivers. The lowest concentration was

recorded at upstream of both rivers. This clearly showed that

both slaughterhouses wastewater plays substantial role in

deterioration of water quality of the corresponding river.

Regardless of the sampling point, all of the parameters ex-

amined except pH, were found much higher than the national

and international drinking water recommended standards

(Table 4). This could be attributed to discharge of diffused

sources from both municipal and industrial liquid and solid

waste of Addis Ababa city to Little Akaki River [7] and from

Modjo town to Modjo River [8] in addition to the slaughter-

houses effluents.

As it can be seen from Table 4 most of the physicochemical

parameters, excluding EC, TS, TSS and NH3 at the discharge

point; EC, TS and COD at the upstream and EC, TS, color

and NH3 at downstream of Modjo River were found in high

concentration, but all the rest parameters were registered

highest in the corresponding sampling points of Little Akaki

River than Modjo River. This variation of pollutants concen-

trations of the two rivers might be attributed to the variation

in amount of discharged effluent, i.e. effluent of municipal

and industrial wastes from Addis Ababa city is much higher

due to the high population, urbanization and industrialization

in the city than the small town Modjo. As a result the water

quality of Little Akaki River is highly deteriorated than Mod-

jo River, and this situation was aggravated by the discharges

of untreated Kera slaughterhouse wastewater.

Again from Table 4 except pH and Temperature, all the phy-

sicochemical parameters of the untreated wastewater (Kera

slaughterhouse) and partially treated wastewater (Luna

slaughterhouse) do not comply with the EEPA and UNIDO

slaughterhouse effluent discharge limit into surface waters

[17]. This indicates that discharging such effluents devastate

the receiving environment.

Table 4: Comparison of the mean value of physicochemical parameters slaughterhouse effluent discharged with standard permit

limits and both Rivers water quality with WHO and Ethiopian drinking water quality

Pa

ram

ete

rs

Slaughterhouses

discharged effluent

Discharge

Permit limit

Modjo River Little Akaki River Drinking water quality

standards

Luna Kera

EPA P3 P4 P5 K2 K3 K4 Ethiopian

(QSAE,2001)

WHO

(2008)

Sulfide (mg/L) 0.144 1.837 -

0.19 0.20 0.11 0.38 0.38 0.37 - -

Color (TCU) 728.667 19733.333 -

523.33 116.00 1973.66 2030.00 676.66 1530.00 15 <15

PH (pH units) 6.81 7.300 6 – 9

6.91 7.46 7.41 6.84 7.47 7.33 6.5-8.5 6.5-8

Temp (ح ) 22.092 26.550 40 C

24.93 22.45 21.50 23.63 23.71 23.20 - -

DO (mg/L ) 0.979 3.753 -

1.67 0.43 0.90 0.14 0.13 0.10 - -

EC( Scm-1 ) 3850 1614.667 -

2930.00 1564.66 2676.66 1235.33 1245.33 1290.33 - -

Turbidity

(JTU=NTU)

160.333 566.667 -

416.66 134.66 285.53 483.33 350.00 420.00 5 5

TS (mg/L ) 1176 7885.333 -

2331.33 932.00 1504.66 1248.66 725.33 913.33 - -

TSS (mg/L ) 125.667 3835.333 80

886.00 154.00 323.00 456.00 304.33 456.00 - -

TP (mg/L ) 61.733 202.000 5

46.13 0.85 18.03 75.33 20.50 26.18 - -

PO4-3(mg/L ) 28.267 67.333 -

28.00 0.46 8.00 9.60 10.26 16.70 - -

NO2- - N

(mg/L)

49.333 1513.333 -

220.00 26.66 144.00 283.00 153.33 597.0 3 3

NO3- - N

(mg/L)

13.667 1450.000 -

28.66 6.26 42.66 110.00 140.33 120.33 50 50

NH3 – N

(mg/L)

345.667 103.333 -

212.33 10.66 115.00 47.33 41.25 47.91 - -

SO4-2 (mg/L ) 31.333 693.333 -

103.33 22.66 40.66 61.33 54.66 52.00 250 -

COD (mg/L ) 431.667 11546.667 250

1080.00 295.00 578.00 1373.33 260.00 623.33 - -

BOD (mg/L ) 177.333 3980.000 80 265.667 84.000 199.333 555.333 95.666 300.66 - -






FOG (mg/L ) 344.76 1825.31 15

389.05 169.07 317.65 739.52 316.83 652.0 - -

FC (cfu) 1.08

x105±2.

103

x104

1.35

x106±3.72

2 x105

-

9.73

x104

3.77

x104

4.93 x104 6.83 x106 6.70

x106

6.97

x106

0 0

TC ( cfu) 4.01

x105±1.

241

x105

4.40x106±

1.114 x106

400

3.58

x105

4.73

x104

1.03 x105 2.13 107 2.10

x107

8.73

x107

0 -

6. Conclusion and Recommendations

The untreated and inadequately treated effluents from both

slaughterhouses have a considerable effect on the water qual-

ity of the receiving water bodies. The levels of most parame-

ters monitored were generally higher in the discharge point of

both rivers. Thus cause many fold increase at downstream of

both rivers. This study suggests that there is a need of remed-

iation of the rivers. There should also be an intervention of

appropriate regulatory bodies (EPA) to ensure production of

high quality treated final effluents by the slaughterhouses

industries and protect the natural surface waters quality.

7. Acknowledgements

I would like to express my gratitude to Center for Environ-

mental Science, School of Graduate Studies, Addis Ababa

University for its financial and laboratory facilities support.

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